The Interrelations of Inversions, Heterosis and Recombination

Abstract

Nversions largely prevent effective recombination in heterozygotes. One result is that, in populations heterogeneous for sequence, the separate sequences will come to differ in the deleterious recessives they carry. Therefore more sequence heterozygotes will survive than would be the case with random mortality. There will be selection in favor of diversity of sequence. This raises the question, why is crossing over (and recombination) not regularly wholly suppressed? Analysis indicates that selection may operate to favor recombination as a means of maintaining the "flexibility" of the species under inconstant environmental conditions; but at least 3 different environmental situations must be assumed, each being recurrent and each decisive (at times) for the fate of at least one generation of individuals.